ToxWatch Monitoring Data Study 2006-2015

ToxWatch is an ambient air quality monitoring program conducted by the Office of Air Quality (OAQ) within the Indiana Department of Environmental Management (IDEM). The program actively monitors air toxic concentrations at various monitoring sites within the state of Indiana. At any given time there are approximately 10 active monitoring sites within the state. The study presented here pulled air toxic concentration readings that were collected over a ten year period from 2006-2015. The monitoring sites selected were those which were active at the end of 2015 and those which were active for at least half of the study period. Based on this criteria, the following locations and monitoring years were included:

County City Monitor Site Name Monitoring Years
Lake East Chicago East Chicago Water Filtration Plant 2006-2012
East Chicago Marina 2013-2015
Gary Gary IITRI 2006-2015
Hammond Hammond CAAP 2006-2015
Whiting Whiting High School 2006-2015
Porter Ogden Dunes Ogden Dunes – Diana Rd 2006-2015
Tippecanoe Lafayette Lafayette Cinergy 2008-2012
Vigo Terre Haute Terre Haute – Fort Harrison Rd 2014-2015
Marion Indianapolis Indianapolis – Washington Park 2006-2015
Vanderburgh Evansville University of Evansville 2006-2015
Clark Clarksville Clarksville – Falls of the Ohio 2008-2015

IDEM’s OAQ laboratory collects samples from monitoring sites on a 1-in-6 day schedule and analyzes the samples using U.S. EPA Method TO-15 for concentrations of 61 different air toxics. For this study, data for each air toxic was pulled and a detection rate was determined. The detection rate is defined as the percentage of valid samples taken statewide that had a quantifiable concentration of the pollutant. Quantifiable concentrations are determined by the OAQ laboratory for each pollutant analyzed. For each pollutant where the detection rate was 50% or higher, an analysis of concentration trends and hazard risk was performed. If the detection rate was below 50% for a pollutant, this analysis was not performed due to the limited amount of quantifiable data.

For pollutants where the detection rate was 50% or higher, data sets for that pollutant were imported into U.S. EPA’s ProUCL 5.0 software to determine the 95% upper confidence limit (UCL) of the mean. A 95% UCL represents a value which one can be 95% confident that the true mean of the population is below that value. There are several different distribution methodologies that can be used to arrive at this value. For purposes of this study, the 95% Student’s-t UCL distribution was utilized. The 95% UCL value was determined for each year a monitor was active in this study and the resulting values were charted and evaluated for trends.

In addition to the individual years, a 95% UCL value was also determined using the full data set for each monitoring site. The 95% UCL value for the full data set was then divided by a benchmark threshold at which a chronic (lifetime) non-cancer hazard can be observed. The resulting ratio is called the hazard quotient for the pollutant at that monitoring site. If the pollutant is a known carcinogen, the 95% UCL value for the full data set was also multiplied by cancer slope factors to determine the additional lifetime cancer risk. Details of the calculated hazard quotient and additional lifetime cancer risk can be found in the report for each individual pollutant. Available emissions data for each pollutant is also noted using 2014 data from the National Emissions Inventory (NEI).

Full study reports for each individual pollutant are provided. The Monitoring page provides additional information about the IDEM Air Monitoring Program. The Air Toxics Monitor Siting page provides information about current air monitoring sites.

Full Study Reports

Pollutants With Concentration Trends (detection rate of 50% or higher)
Pollutants Without Concentration Trends (detection rate less than 50%)